1. Field of the Invention
The invention relates to a method for measuring and correcting the plunger depth adjustment in a high-speed stroke press and circuitry for implementing such method.
2. Description of the Prior Art
It has been known from high-speed presses which perform a machining operation that the plunging depth of the upper tool into an associated lower tool increases with increasing operating speed, thus altering considerably the required tolerances of the press both for cutting or punching processes and for bending or embossing work, and influencing them in a negative sense. But not only the semi-finished products or the like to be produced suffer from the plunger misadjustment, but the tools will be subject to increased wear, thus resulting in unavoidable downtimes and increased tooling expenditures.
A circuitry is disclosed in DE-PS No. 27 31084 by means of which the actual plunging depth of such a plunger is determined by inductive measurement permitting a subsequent comparison between actual and specified values in order to effect the required correction. There, the plunger adjustment is corrected by means of a motor at stroke numbers exceeding 600 strokes per minute, the motor acting upon a stroke bearing setting member through a gear train with high speed reduction by means of which the plunger is adjustable with respect to its driving mechanism, thus modifying the plunging depth, i.e., it may be corrected as required. Instead of the current actual-value measurement of the plunging depth, in this known circuitry a correction may be made by means of a program stored in a memory, setting signals being fed to one-shot multivibrators in accordance with the program depending on the number of strokes, which in turn activate the correction motor in accordance with the signal information units.
Another known circuitry for a setting drive of a plunger adjustment (DE-PS 28 33 929) uses at least one limit switch, placed settable in the operative path of the plunger on the press frame for reading the plunging depth, and the signal output of which is connected to the set input of a first flip-flop, the signal output of which is back-fed to the reset input of another flip-flop through of a branch line via a switch step determining the amount of an adjustment step; a set input of still another flip-flop being connected to a switch which is activated on interruption of the operation of the cutting press, and a reset input of the latter flip-flop being connected to another switch which is activated whenever the plunger reaches its lowermost position with respect to its drive mechanism, which it must not fall short of, depending on the tool.
The two known circuitry arrangements have the advantage that the plunger adjustment is possible during the operation of the press, but on the other hand, they have the substantial disadvantage that the circuitry arrangements are very expensive requiring a correspondingly high expenditure both for the hardware and for the software.